Security source: We’re assuming the teenagers are alive; Kerry: This was a despicable act of terrorism; Army issues limited call-up of reservists.

Hamas abducted the three missing teenagers, Prime Minister Binyamin Netanyahu said Sunday as the IDF issued a limited call up of its reservists to intensify the army’s operations against the terrorist group.

Most of the reservists are heading to Hebron to help the IDF maintain its newly imposed closure on the city and to step up the army’s hunt for the teenagers, who disappeared last Thursday night while hitching a ride in Gush Etzion.

At the same time, the air force deployed a number of Iron Dome anti-rocket batteries in southern Israel to prepare for any escalation of its battle with Hamas, which rules the Gaza Strip and has strengthened its foothold in the West Bank.

“Hamas terrorists carried out Thursday’s kidnapping of three Israeli teenagers. We know that for a fact,” Netanyahu said.

According to Palestinian information published on Sunday, two top Hamas operatives have disappeared from the West Bank since Thursday.

Also on Sunday, it was revealed that one of the teenagers made a desperate phone call to the police late Thursday night to say: “We’ve been kidnapped.” The police ignored the call for several crucial hours.

“Our working assumption is that the teenagers are alive. We are working to bring them back alive,” a senior security source said.

On Sunday night, thousands gathered at the Western Wall to pray for the teens’ safe return. Dozens of other prayers services took place across the country, including at the Cave of the Patriarchs in Hebron and at the Makor Haim Yeshiva in Kfar Etzion, where two of the teens studied.

While the families waited for news, the IDF conducted house-to-house searches in Hebron as it scoured the city, where Hamas has a strong foothold.

As of late Sunday night, the IDF had arrested over 80 Hamas members in the West Bank, including Hamas leader Hassan Youssef and members of the Hamas’s legislative council.

US Secretary of State John Kerry on Sunday “strongly condemned” the kidnapping as a “despicable terrorist act,” and called for the release of the three teenagers, one of whom, Fraenkel, has dual Israeli-American citizenship.

Kerry more cautiously agreed that “many indications point to Hamas’s involvement.” But, he said, the US has yet to make that determination and still seeks more details.

“We reiterate our position that Hamas is a terrorist organization known for its attacks on innocent civilians and which has used kidnapping in the past,” said Kerry, adding that “we continue to offer our full support for Israel.”

Hamas spokesman Sami Abu Zuhri said on Facebook that Netanyahu’s charges against his group were “stupid with an intelligence dimension.”

Israel alone bears responsibility for the “escalation against our people and their leaders in the West Bank,” he said.

Hamas’s denials do not change the fact that it is an organization dedicated to Israel’s destruction, Netanyahu said in a statement issued in English for an international audience.

The prime minister charged that the Fatah-Hamas unity pact and the international endorsement it received were responsible for creating a climate that enabled the kidnapping.

“I believe that the dangers of that pact now should be abundantly clear to all,” said Netanyahu, adding that terrorism emanating from the West Bank has risen since it was signed.

“We have seen Hamas strengthen its presence there, and this increases the likelihood that Hamas will take control of the Palestinian Authority, precisely as it did in Gaza,” Netanyahu said.

He said that he holds Palestinian Authority President Mahmoud Abbas responsible for the kidnapping, because he partnered with Hamas while failing to disarm it.

“The Palestinian claim that the Palestinian Authority cannot be held responsible for an attack that took place in an area under Israeli security control is patently absurd,” Netanyahu said.

”When an attack takes place in Tel Aviv or in London or in New York – all these places have been attacked by terrorists – the question is not where the attack takes place. The question is where it originated. The kidnappers in this case set out from territory controlled by the Palestinian Authority, and the PA cannot absolve itself of its responsibility,” he said.

The prime minister warned that Israel would take any action necessary to protect its citizens.

“Israel will act against the kidnappers and their terrorist sponsors and comrades. We will do whatever needs to be done to protect our people, our citizens, our children and our teenagers from the scourge of terrorism,” Netanyahu said.

He made similar comments earlier in the day before the weekly cabinet meeting, which was held at the defense compound in Tel Aviv, rather than in its regular Jerusalem location at the Prime Minister’s Office.

The night before, the prime minister convened the security cabinet, which decided to close the city of Hebron and the passages from Israel into the Gaza Strip except for humanitarian reasons such as medical emergencies.

The military declared a closure in parts of the Judea region, from Bethlehem southward.

Hebron has been under closure since Saturday evening in a “partial geographic isolation,” an army source said. The closure is not complete in order to avoid harming Palestinian civilians or their economy, according to the source.

“The aim of this activity is to tighten the circle the of intelligence,” he said, adding that levels of violence in the West Bank remained under control, with one pipe-bomb attack reported in Kalandiya and sporadic rock throwing.

Large numbers of infantry soldiers, including paratroopers and Kfir battalions, as well as many intelligence units, are on the ground, continuing to expand the operation. Soldiers moved throughout the southern West Bank area, checking Palestinian vehicles. Special forces conducted raids of homes, making arrests and carrying out search.

A senior military source said the operational pattern of the kidnappers is “certainly complex and different,” indicating that a terrorist organization was behind the attack.

“We have a lot of knowledge on Hamas in Hebron,” the source said. “Dozens of kidnapping attempts have been thwarted [this year],” he added. “There is a knowledge infrastructure, and the Shin Bet (Israel Security Agency) has intelligence assessments [on the kidnappers].”

Hamas in the West Bank is in a difficult situation, the source continued, saying the organization is struggling in general to carry out suicide bombings and kidnappings despite trying.

“It is under pressure. At the same time, that’s not enough to lower its motivation,” he added. The motivation for terrorists to carry out terror attacks remains very high, he said.

The kidnapping is “an incident with the potential for escalation. Our challenge is to prevent an escalation,” he said.

The Hamas spokesman said that the IDF’s arrest of more than 100 Hamas and Islamic Jihad member and officials in the West Bank on Saturday night was a sign of the “wallowing” in Israel in the aftermath of the abduction of the youths.

In a statement published in the Gaza Strip, Hamas said that the IDF crackdown on its men would not stop the movement from pursuing its fight to “liberate Palestine.”

Hamas urged Palestinians in the West Bank to step up their “resistance and expand confrontations with the occupation” to help the kidnappers.

Hamas called on the Palestinian Authority to halt security coordination with Israel and to “side with the choices of our people and their resistance groups.”

The statement saluted the “heroes” who kidnapped the three youths.

Meanwhile, sources in the Gaza Strip said that several Hamas leaders have gone into hiding following Israel’s charges that the movement was responsible for the kidnapping of the three teenagers.

The Palestinian Islamic Jihad organization on Sunday warned Israel against continuing its security crackdown on Palestinians in the West Bank.

The group said that Israel was using the abduction as an excuse to justify its “aggression against the Palestinian people,” adding that it would respond with full force to the ongoing Israeli security measures.